Refactor: Use a constant instead of the magic 50
Refactor: Use a constant instead of the magic 50

We used the magic constant 50 in the source code a number of
places for the item search. This patch refactor that to a
constant with a description.

daverigby/kv_engine,owendCB/memcached,abhinavdangeti/memcached,daverigby/memcached,zbase/memcached,zbase/memcached,daverigby/kv_engine,abhinavdangeti/memcached,zbase/memcached,Metaswitch/memcached,Metaswitch/memcached,mrkwse/memcached,abhinavdangeti/memcached,zbase/memcached,abhinavdangeti/memcached,mrkwse/memcached,zbase/memcached,couchbase/memcached,cloudrain21/memcached-1,daverigby/memcached,Metaswitch/memcached,owendCB/memcached,Metaswitch/memcached,cloudrain21/memcached-1,daverigby/kv_engine,daverigby/memcached,cloudrain21/memcached-1,couchbase/memcached,Metaswitch/memcached,jimwwalker/memcached,jimwwalker/memcached,mrkwse/memcached,owendCB/memcached,daverigby/kv_engine,owendCB/memcached,couchbase/memcached,cloudrain21/memcached-1,jimwwalker/memcached,daverigby/memcached,mrkwse/memcached,couchbase/memcached,abhinavdangeti/memcached